I'm having the exact same problem. I don't think you are doing anything wrong because it pulls up the Khan Academy page, there is just nothing there except for their logo graphic header and that message.

https://www.edu-apps.org/lti_public_resources/?tool_id=khan_academy#/khan_academy/browse/root

No resolution as of yet.

Having this problem too.

Same.  It says "dashboard" and there are no videos available.  If I click on the "dashboard" it does nothing.

That is exactly what I see on my Canvas.

Same!!! Please help!

From Khan Academy support:

"I'm afraid that Khan Academy's exercises and courses cannot be embedded outside of the platform, and must be completed through the Khan Academy website. Any grades or scores achieved in Khan Academy cannot be reflected onto an LMS (or even Google Classroom) either. We are making numerous changes as we transition to a new technical platform. As part of this work, we stopped supporting the public API in 2020. As a result, any calls that you make to our API after that point will return errors that you already have encountered.

Khan Academy does not currently support integrations with any LMSs, including Canvas. That said, you should be able to embed URLs of Khan Academy videos hosted on YouTube and, additionally, you can always link directly to any lesson or exercise URLs found on our site and have it redirect your students from the LMS to khanacademy.org."

[Emphasis added]

Oh My Goodness!!! Way to kick educators when we are down!  I am done with Khan Academy!!!  I will never donate to them again.  I will never use their content in my classes again.  Of all times, during the middle of this pandemic that is forcing teachers all across the country to participate in virtual learning, they stopped supporting the public API.   I used to believe that Khan Academy truly believed in education... Now they show themselves to be just another greed monger.  Instead of supporting educators, they kick your knees out from under you!

That's too bad. I can't believe we lost the API at the second that I started making lessons on Canvas.

Incredibly frustrated by this. I have dozens of assignments and quizzes that have integrated Kahn videos that I will now have to change. So many schools and districts are using Canvas K-12 and we don't have a choice but to have all navigation flow through it. YouTube is blocked in my district so accessing videos that way is a huge pain. I have really appreciated this site the past few years, but this is really frustrating.

Is this still the case or is there new information regarding this issue